linux-kernel - Re: gcc-10: kernel stack is corrupted and fails to boot

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Date:   Wed, 13 May 2020 15:45:47 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Kalle Valo <kvalo@...eaurora.org>
Cc:     linux-wireless <linux-wireless@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: gcc-10: kernel stack is corrupted and fails to boot

On Wed, May 13, 2020 at 2:57 PM Kalle Valo <kvalo@...eaurora.org> wrote:
>
> Arnd Bergmann <arnd@...db.de> writes:
>
> > On Wed, May 13, 2020 at 8:50 AM Kalle Valo <kvalo@...eaurora.org> wrote:
> >>
> >> Kalle Valo <kvalo@...eaurora.org> writes:
> >
> > At least if it fails reproducibly, it's probably not too hard to drill
> > down further. Some ideas:
> >
> > * I'd first try to reproduce it in qemu. Since you don't even need
> >   any user space or modules, I would simply try
> >   $ qemu-system-x86_64 -nographic -monitor none -append
> > "console=ttyS0" -serial stdio -smp 4 -kernel arch/x86/boot/bzImage
> >   I tried it here with an x86 defconfig linux-next kernel but did not
> >   run into the problem you described.
>
> Thanks, I'll try that but I expect it will take few days before I can do
> it.
>
> > If you share your .config, I can try reproducing with that as well.
> > Once there is a reproducer in qemu, it should be trivial to step
> > through it using gdb.
>
> I have attached the .config I used with GCC 10.1. If you are able to
> test it please do let me know how it went.

Yes, I see the same problem now, but have not investigated
any further.

> > * There are still two prerelease compiler versions on kernel.org,
> >   from February and from April. You can try each one to see
> >   if this was a recent regression. It's also possible that there is
> >   a problem with my specific builds of gcc-10.1, and that the
> >   compiler is actually fine for others.The gcc-10 packages in
> >   Fedora/Debian/Ubuntu are probably better tested.
>
> I'm still using Ubuntu 16.04 so not sure how easy it is to find a
> package for that, but maybe this is a good reason to finally my upgrade
> my laptop :)

I checked with the gcc-10 package from Ubuntu 20.04, same
result as with my version, at least that indicates it's not my fault ;-)

      Arnd